* KGHM recognises $494 mln loss after impairment tests
* Group also books $510 mln loss on key Sierra Gorda asset
* One-off losses stem from commodity price slump
* KGHM maintains dividend policy despite losses (Adds more detail, company comments)
WARSAW, Feb 8 (Reuters) - Poland's KGHM, Europe's second-biggest copper producer, on Monday flagged a record $1 billion in writedowns on key foreign assets, including the Sierra Gorda mine in Chile, due to plunging metals prices.
The state-controlled group said the writedowns will not impact its dividends and credit covenants, adding that it has begun revising its 2015-2020 strategy to significantly reduce capital needs in the short and medium term.
The move is the latest in a series of writedowns on resource assets and downgrades of earnings forecasts by miners in the face of a global commodity slump.
KGHM, which closed the first three quarters of the year with a consolidated net profit of 1.2 billion zlotys ($301.6 million), recognised a $494 million loss following impairment tests on its assets in Chile, the United States, and Canada.
It also announced a $510 million loss on its investment in the Sierra Gorda SCM firm that owns the Sierra Gorda mine - KGHM's largest foreign asset - bringing the group's total impairments for the year to just over $1 billion.
KGHM, also the world's largest silver miner, has been hit by persistently low commodity prices in the face of worries about Chinese demand. Copper prices fell to their lowest since mid 2009 last month.
The group, which ended the third quarter of 2015 with its ratio of net debt to core profit at 1.0, said it wants to cap the ratio at below 2.0 in order to make a planned dividend payout from 2015 stand-alone profit.
"I believe that in the longer term KGHM's assets will show the envisaged investment returns," KGHM's newly appointed chief executive, Krzysztof Skora said in a statement.
KGHM gained control of Sierra Gorda in 2011 when it bought Canadian rival Quadra FNX for C$2.87 billion ($2.07 billion), the largest ever foreign acquisition by a Polish company. The mine launched commercial production only last year.
Last week Sierra Gorda's co-owner, Japan's Sumitomo , said it cut its profit forecast due to the investment loss at the Chilean mine.
According to Sumitomo, Sierra Gorda produced about 85,000 tonnes of copper concentrate in 2015 and aims to reach full utilisation by the end of June. ($1 = 1.3882 Canadian dollars) ($1 = 3.9793 zlotys) (Reporting by Adrian Krajewski and Marcin Goettig; Editing by Jan Harvey)